In English, "the Amazon" could also be a valid phrase apart from the river. For instance, you might have a course called "The Amazon in Ancient Greek and Modern Culture".
No, it would still be "The Amazons from Ancient Greece" or "The Greek Amazons" or something. "Amazon" singular in that context is only used as an adjective, such as "the Amazon Queen".
Quick edit: Ah wait, I think I see what you're doing with that phrase. It's shorthand for "The Amazon culture" or "Amazon depictions" or something, but it still comes off as strange-sounding to me.
Using "the X" to generalize about a group of people is likely to trigger offense if you're talking about a group of people who exist or is identified with today. It's not just the essence of stereotyping, but also kind of affected and pompous.
So, sure, it sounds "strange", but it's not new, and people use it when they want to make a generalization with a tone of authority. Probably one might expect to get away with it when talking about an abstract concept or archetype that exists independently of actual people.
